Spiral-grooved arrow shaft

ABSTRACT

The present invention is a spirally grooved arrow shaft that imparts axial rotation to an arrow assembly. The shaft has a plurality of substantially identical, helical, longitudinal channels along its outer surface extending down a substantial portion of the arrow shaft along its primary axis. The channels may consist of a plurality of grooves cut into the outer surface of the arrow shaft. Alternatively, the channels may be formed from a plurality of raised-fins or raised members that extend radially outward from the surface of the shaft. The invention is compatible with all contemporary arrowheads and vanes provided that all aerodynamic surfaces present on these devices urge rotation of the arrow assembly in the same direction as the spiral channels.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to the field of archery. Specifically, the invention relates to the arrow shaft component of arrow devices.

2. Description of the Prior Art

The flight path of an arrow assembly must be predictable in order for an archer to strike an intended target. The arrow should not float or drift from the path along which it was aimed.

Prior art arrow assemblies have relied upon the aft or forward end to provide this guidance. The most ancient of these technologies is the uniformly spaced application of two, three, or even more feathers, also referred to as fletches or vanes, about the aft end of the arrow assembly. These fletches steer the arrow assembly from behind like the rudder of a ship. The arrow assembly is essentially pushed through the air. This pushing can cause the flight path of the arrow assembly to wander as the arrow assembly is affected by random influences such as crosswind, oscillating vibration of the arrow shaft, and asymmetries between the arrow vanes' mass or installation position. One recent improvement is the vane of Kuhn (U.S. Pat. No. 6,695,727) that employs vanes whose geometry imparts an axial rotational spin on the arrow assembly during flight

The use of aerodynamic influences at the forward end of an arrow assembly has been less deliberate in the prior art until recently. So-called field point arrowheads are very simple devices that are commonly used for target practice. Field point arrowheads taper from a maximum diameter, equal to approximately the diameter of the arrow shaft, down to a point at the forwardmost end. This prior art arrowhead has a negligible aerodynamic effect as the arrow assembly flies towards its intended target.

Broadhead arrowheads were invented to increase effective hunting penetration and success potential. Typically two to four flat, triangular blades are arranged around the forward pointed tip. These broad, flat blades have a pronounced aerodynamic effect that can radically affect the overall stability of the arrow in flight and significantly reduce the precision of flight. Typical incarnations of such broadheads are described in the patents of Newnam (U.S. Pat. No. 5,636,845) or Musacchia (U.S. Pat. No. 4,621,817). One recent improvement is the broadhead of Kuhn (U.S. Pat. No. 6,663,518) that employs blades whose deliberate, aerodynamically active geometry imparts an axial rotational spin on the arrow assembly during flight. Such inventions are improvements over the fletching technologies because they provide steering from the leading end of the arrow. Asymmetries encountered during flight tend to be damped out by the trailing rotational inertia of the shaft. One drawback of these technologies is that the arrowheads can be easily damaged and may be rendered useless after a single shot. Manufacturing tolerances must also be strict in order to produce a product that has consistent aerodynamic qualities.

Spin-stabilization is clearly a desirable feature for any successful arrow assembly. Unfortunately, the competing aerodynamic effects of the aft end and forward end enhancements described above can render each other unsuccessful. Furthermore, individual archers may prefer features found in certain vanes or arrowheads; such features may not be included in commercially available products. The prior art lacks teaching of a spin-stabilizing arrow shaft as a part of an arrow assembly. Such a shaft could be assembled with an archer's choice of vanes and arrowhead while still providing adequate spin stabilization to promote accurate flight.

SUMMARY OF THE INVENTION

The present invention is a spirally grooved arrow shaft that imparts axial rotation to an arrow assembly. The shaft has a plurality of substantially identical, helical, longitudinal channels along its outer surface extending down a substantial portion of the arrow shaft along its primary axis. The channels may consist of a plurality of grooves cut into the outer surface of the arrow shaft. Alternatively, the channels may be formed from a plurality of raised fins or raised members that extend radially outward from the surface of the shaft. The invention is compatible with all contemporary arrowheads and vanes provided that all aerodynamic surfaces present on these devices urge rotation of the arrow assembly in the same direction as the spiral channels.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an oblique longitudinal view of the present invention.

FIG. 2 shows a cross-sectional view of a first embodiment of the present invention. The cross-section is perpendicular to the major axis of the arrow shaft.

FIG. 3 shows a cross-sectional view of a second embodiment of the present invention. The cross-section is perpendicular to the major axis of the arrow shaft.

DETAILED DESCRIPTION OF THE INVENTION

With reference to FIGS. 1 through 3, arrow shaft 1 of the invention comprises a typically cylindrical body of substantially uniform diameter with a first end 2 and a second end 3. Shaft 1 is typically symmetrical about the longitudinal axis and may be manufactured from any suitable structural material known in the art such as steel, aluminum, carbon fibers, plastic or a composite of materials. Any arrowhead known in the art may be attached by typical attachment means (not depicted) to first end 2. Typically, such an attachment means comprises a female-threaded socket that is press-fitted or glued into first end 2 of arrow shaft 1. This socket mechanically engages the arrowhead to arrow shaft 1. Any fletches known in the art may be attached to second end 3 by typical attachment means known in the art such as gluing.

At least one helical channel 4 begins at first end 2 of arrow shaft 1 and spiral down the longitudinal axis of arrow shaft 1 toward second end 3. Helical channels 4 are integral to arrow shaft 1 and disposed on the outer surface of arrow shaft 1. Field tests suggest that a right-handed spiral pitch equal to one turn in twenty-four inches of shaft length down the longitudinal axis works well, but other pitches and left-handed spirals are also envisioned within the scope of the invention.

In a first embodiment, helical channels 4 are formed either by cutting or extruding grooves of v-shaped or square cross section into the smooth outer surface of arrow shaft 1, although other groove geometries would be obvious to one of ordinary skill in the art. Helical channels 4 are defined as grooves if the minimum diameter of the channeled portions of arrow shaft 1 does not exceed the nominal maximum diameter of arrow shaft 1. Helical channels 4 do not penetrate entirely through the wall of arrow shaft 1. In the preferred embodiment, helical channels 4 are only cut through the gel coat and outer layer(s) of the formed arrow shaft 1.

In a second embodiment, helical channels 4 are formed between raised helical ridges 5 of v-shaped or square cross section that are integral with the outer surface of arrow shaft 1. Other ridge geometries would be obvious to one of ordinary skill in the art. Helical channels 4 are defined as the space between a pair of ridges 5 if the maximum diameter of the ridged portions of arrow shaft 1 exceeds the nominal maximum diameter of arrow shaft 1. Helical ridges 5 are formed by extrusion with or physical application onto the smooth outer surface of arrow shaft 1. Helical ridges 5 extend radially outward from the outer wall of arrow shaft 1.

Helical channels 4 may spiral down substantially the entire axial length of arrow shaft 1, or they may terminate partially down a portion of the axial length of arrow shaft 1. In the preferred embodiment, helical channels 4 terminate between about three and about five inches short of second end 3. This provides a smooth surface of arrow shaft 1 for the physical application of fletches.

All helical channels 4 spiral in the same rotational direction giving the appearance of a turbine. In the preferred embodiment, helical channels 4 are disposed close together around arrow shaft 1 so that they are adjacent to each other down their entire helical length.

In the preferred embodiment there are between about three and about ten helical channels 4 located symmetrically about the circumference of arrow shaft 1. There are optimally about eight helical channels 4 located symmetrically about the circumference of arrow shaft 1. Too few helical channels 4 will not provide enough rotational torque to produce the desired axial flow turbine aerodynamic effect. Too many helical channels 4 must be so narrow or small that their aerodynamic effect becomes inconsequential as their aggregate surface approaches that of a smooth arrow shaft.

One of the features of this invention is its ability to produce stabilized arrow assembly flight without the use of fletches or tail fins (or feathers). The rotation induced in the arrow assembly by the aerodynamically designed arrow shaft is sufficient to stabilize the arrow in flight. Eliminating or reducing the size of the fletches in fact improves flight characteristics because the rotational drag normally induced by the fletches is avoided. It should be noted, however, that all embodiments of the arrow shaft of the invention can be used with fletches as well.

While various embodiments of the present invention have been described above, it should be understood that they have been presented by way of example only, and not limitation. Thus, the breadth and scope of the present invention should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents. 

1. An arrow shaft including: a first end; a second end; and at least one helical channel disposed on the outer surface of said arrow shaft; and wherein said at least one helical channel begins at said first end of said arrow shaft and spirals down the longitudinal axis of said arrow shaft toward said second end; and wherein all said channels spiral in the same rotational direction giving the appearance of a turbine.
 2. An arrow shaft according to claim 1, wherein said helical channels consist of grooves in the smooth outer surface of said arrow shaft.
 3. An arrow shaft according to claim 1, wherein said helical channels are formed between raised helical ridges in the smooth outer surface of said arrow shaft; wherein said helical ridges are integral with the outer surface of said arrow shaft; and wherein said helical ridges extend radially outward from the outer wall of said arrow shaft.
 4. An arrow shaft according to claim 1, wherein said channels are close together around said body so that they contact each other down their entire helical length said helical channels are disposed close together around said arrow shaft so that said helical channels are adjacent to each other down their entire helical length.
 3. An arrow shaft according to claim 1, wherein there are between about three and about ten said channels located symmetrically about the circumference of said arrow shaft.
 4. An arrow shaft according to claim 1, wherein there are eight said channels.
 5. An arrow shaft according to claim 1, wherein said channels terminate partially down a portion of the axial length of said arrow shaft. 